Federal drug regulators believe that a contaminant detected in a crucial blood thinner that has caused 81 deaths was added deliberately

Do you remember the horrible poisoning of Tylenol in 1982? Seven people died in the Chicago area after taking off the shelf Tylenol that had been laced with cyanide. Well, get ready, because it looks like we're in for the same kind of ride... but this time much bigger.

Federal drug regulators believe that a contaminant detected in Heparin, a crucial blood thinner, has caused 81 deaths was added deliberately, something the Food and Drug Administration has only hinted at previously.

“F.D.A.’s working hypothesis is that this was intentional contamination, but this is not yet proven,” Dr. Janet Woodcock, director of the Food and Drug Administration’s drug center, told the House Subcommittee on Oversight and Investigations in written testimony given Tuesday.

A third of the material in some batches of the thinner heparin were contaminants, “and it does strain one’s credulity to suggest that might have been done accidentally,” Dr. Woodcock said.

The hearing on Tuesday was also the first in which family members of those who died were asked to testify.

LeRoy Hubley described how both his 65-year-old wife and his 47-year-old son died within a few weeks of each other. Both suffered from a genetic kidney disease that required constant dialysis, for which heparin is routinely used.

“Now I am left to deal not only with the pain of losing my wife and son, but anger that an unsafe drug was permitted to be sold in this country,” he said.

The chief executive of Scientific Protein Laboratories (the company that supplied contaminated heparin material to Baxter International, which manufactured and distributed the finished drug), David G. Strunce, described the contamination as “an insidious act” that “seems to us an intentional act upstream in the supply chain.”

Mr. Strunce said that his company tried to find the original source of the contamination but was stopped by the Chinese authorities.

Chinese officials have disputed the F.D.A. contention that the contaminant caused death and injury, and they have insisted on the right to inspect American drug plants if the F.D.A. insists on inspecting Chinese ones.

David Nelson, a Congressional investigator, told the House panel that had the F.D.A. inspected the Chinese plant, the contamination could have been averted.

F.D.A. officials have admitted that they mistakenly failed to conduct an inspection of the Changzhou SPL plant but said that an inspection would not have been able to uncover the contamination.

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